1. Field of the Invention
The present invention relates to a printing apparatus and processing method therefor.
2. Description of the Related Art
There is known a printing apparatus that has a so-called full-line printhead, whose printing width corresponds to a printing medium width. In a printhead of this type, a plurality of printheads are arranged with a shift in the nozzle arrayed direction. A printing apparatus having such a printhead can print an image on almost the entire surface of a printing medium by relatively moving the printhead once with respect to the printing medium.
If an error occurs in the mounting position of the printhead or the relative mounting positions of a plurality of printheads in the full-line printhead, the ink landing position (attached position) may shift owing to the error. This shift degrades the printing quality.
To cope with the shift of the landing position, Japanese Patent Laid-Open No. 2004-181697 discloses the technique of reading a test pattern using a CCD line sensor, and correcting the landing position based on the reading result.
In contrast, Japanese Patent Laid-Open No. 2010-105203 discloses a technique of calculating the relative positions of patterns using pattern matching. This technique can shorten the adjustment time and decrease the test pattern length because it is sufficient to perform adjustment only once. More specifically, the same pattern is repeatedly printed on a printing medium and read using a CCD line sensor, measuring the relative distance between the patterns.
A case in which a test pattern is formed on a printing medium using a printhead, and read on the downstream side of the printhead while conveying the printing medium will be examined. In this case, a printing medium conveyance shift may occur in the arrangement disclosed in Japanese Patent Laid-Open No. 2004-181697. When the conveyance shift occurs, the test pattern size changes, failing to accurately read the test pattern. In the arrangement disclosed in Japanese Patent Laid-Open No. 2010-105203, the size of a read image differs between patterns to be matched, increasing the measurement error.